**Question:** All are true about osteoarthritis, except

A. Osteoarthritis is a degenerative joint disease characterized by the progressive wearing away of articular cartilage.
B. Osteoarthritis affects primarily the elderly population.
C. Osteoarthritis is caused by trauma or infection.
D. Osteoarthritis primarily affects weight-bearing joints.

**Correct Answer:**

**Core Concept:** Osteoarthritis (OA) is a degenerative joint disease resulting from the gradual wear and tear of articular cartilage, leading to joint pain, stiffness, and limited mobility. OA affects the weight-bearing joints, such as the knees, hips, and spine, but can also involve non-weight-bearing joints.

**Why the Correct Answer is Right:** Osteoarthritis is primarily caused by the aging process and mechanical stress on joints, not trauma or infection. Although it commonly affects the elderly population, it can also occur in younger individuals due to genetic, obesity-related, or other factors. While OA does primarily affect weight-bearing joints, option C, "Osteoarthritis is caused by trauma or infection," is incorrect because these are not the primary etiologies for the disease.

**Why Each Wrong Option is Incorrect:**

**Option A:** While osteoarthritis does involve the wearing away of articular cartilage, stating that it is "the progressive wearing away of articular cartilage" is an oversimplification of the disease process. OA is a complex condition involving various factors like genetics, obesity, and mechanical stress.

**Option B:** While osteoarthritis is more prevalent in the elderly, it can occur in younger individuals as well, making the statement "Osteoarthritis affects primarily the elderly population" partially correct but incomplete.

**Option C:** Osteoarthritis is not caused by trauma or infection. Trauma and infection are risk factors for developing OA, not its primary causes.

**Option D:** While OA primarily affects weight-bearing joints, stating "Osteoarthritis is caused by trauma or infection" is incorrect because these are not the primary etiologies for the disease. The correct statement should be: Osteoarthritis primarily affects weight-bearing joints, such as the knees, hips, and spine.

**Clinical Pearl:** Understanding the etiology and risk factors of osteoarthritis is essential for early diagnosis and management of the disease. OA is a progressive joint disorder that primarily affects weight-bearing joints due to mechanical stress, aging, and genetic factors, rather than trauma or infection.